In the first of three sharp-worded Twitter messages, the EU's Home Affairs Commissioner Cecilia Malmström said an investigation into the "appalling" conditions at Italian detention centres is underway.
In the second, she said: "The EU is committed to assist Italy in receiving migrants, but it has to be done in decent conditions," before adding, "we will not hesitate to launch an infringement procedure to make sure EU standards and obligations are fully respected,"
Her statements come on the eve of a summit expected to touch on the politically sensitive issue of migratory pressure.
Lampedusa has been swamped by an exodus of refugees and migrants washing up in rickety boats. It hit world headlines in October when 300 people drowned off its shores seeking to get to the EU.
Meanwhile, images of Lampedusa shown on Italy's Rai 2 TV this week including troubling shots of naked men being disinfected have set off an outcry there from migrants' rights campaigners.
Figures late October showed more than 13,000 people had sought asylum on Lampedusa this year - more than double the population of the island, located off the coasts of Libya and Tunisia.
The Rai 2 state television report about the Lampedusa migrant centre included a video footage shot secretly by a migrant showing naked men being disinfected in what appears to be an open space.
In a corner of the screen, nurses can also be seen checking the migrants as they queue to be washed down.
Italian Prime Minister Enrico Letta on Tuesday promised to investigate and the mayor of Lampedusa, Giusy Nicolini, said the images reminded her of a "concentration camp".
Migrant centres are run by the national government in Italy and Letta promised an "in-depth" inquiry that would punish those found to be responsible.
Earlier this month the European Union listed proposals aimed at avoiding a repeat of the October 3rd tragedy off Lampedusa when a boat overloaded with refugees, mostly fleeing Somalia and Eritrea, caught fire and capsized.
The proposals are to be put to an EU leaders' summit on Thursday and Friday.
They include beefing up border surveillance, boosting EU assistance to member states facing the biggest influx of migrants, improving the fight against human trafficking and opening more legal channels to reach Europe - including resettling more refugees in the EU.
Immigration charities estimate between 17,000 and 20,000 migrants have died at sea trying to reach Europe in the past 20 years.